Performance of a membrane bioreactor in extreme concentrations of bisphenol A.

In this study, a submerged membrane bioreactor was used to study the effect of low and high bisphenol A (BPA) concentration on the sludge biological activity. The pilot was operated over 540 days with hydraulic retention time and solid retention time of 5.5 hours and 140 days, respectively. As a hydrophobic compound, BPA was highly adsorbed by activated sludge. In lower concentrations, the biodegradation rate remained low, since the BPA concentration in the sludge was lower than 0.5 mg/g TS; yet, at an influent concentration up to 15 mg/L, the biodegradation rate was increasing, resulting in 99% BPA removal efficiency. The result for chemical oxygen demand removal showed that BPA concentration has no effect on the heterotrophic bacteria that were responsible for the organic carbon degradation. In higher concentrations, up to 16 mg of BPA was used for each gram of sludge as a source of carbon. However, the activity of autotrophic bacteria, including nitrifiers, was completely halted in the presence of 20 mg/L of BPA or more. Although nitrification was stopped after day 400, ammonia removal remained higher than 70% due to air stripping. Assimilation by bacteria was the only removal pathway for phosphorus, which resulted in an average 35% of P-PO4 removal efficiency.

Investigation on removal pathways of Di 2-ethyl hexyl phthalate from synthetic municipal wastewater using a submerged membrane bioreactor.

Highly hydrophobic Di 2-ethyl hexyl phthalate (DEHP) is one of the most prevalent plasticizers in wastewaters. Since its half-life in biological treatment is around 25days, it can be used as an efficiency indicator of wastewater treatment plant for the removal of hydrophobic emerging contaminants. In this study, the performance of submerged membrane bioreactor was monitored to understand the effect of DEHP on the growth of aerobic microorganisms. The data showed that the chemical oxygen demand (COD) and ammonia concentration were detected below 10 and 1.0mg/L, respectively for operating conditions of hydraulic retention time (HRT)=4 and 6hr, sludge retention time (SRT)=140day and sludge concentration between 11.5 and 15.8g volatile solid (VS)/L. The removal efficiency of DEHP under these conditions was higher and ranged between 91% and 98%. Results also showed that the removal efficiency of DEHP in biological treatment depended on the concentration of sludge, as adsorption is the main mechanism of its removal. For the submerged membrane bioreactor, the pore size is the pivotal factor for DEHP removal, since it determines the amount of soluble microbial products coming out of the process. Highly assimilated microorganisms increase the biodegradation rate, as 74% of inlet DEHP was biodegraded; however, the concentration of DEHP inside sludge was beyond the discharge limit. Understanding the fate of DEHP in membrane bioreactor, which is one of the most promising and futuristic treatment process could provide replacement for conventional processes to satisfy the future stricter regulations on emerging contaminants.

Biodegradation of Bisphenol-A in aerobic membrane bioreactor sludge.

Bisphenol-A (BPA) biodegradation was studied in a membrane bioreactor under aerobic conditions. The effects of the initial BPA concentration and initial chemical oxygen demand (COD) concentration on BPA biodegradation were investigated. The degradation process followed a first-order kinetic (more than 98% of BPA was removed) with a kinetic rate constant of 1.134 h(-1) using an initial BPA concentration of 1.0 mg L(-1). The kinetic rate constant decreased to 0.611 h(-1) when the initial BPA concentration increased to 5.0 mg L(-1). The initial COD concentration (400 and 2,000 mg L(-1)) did not affect the biodegradation kinetic of BPA.

Contribution of a submerged membrane bioreactor in the treatment of synthetic effluent contaminated by Bisphenol-A: mechanism of BPA removal and membrane fouling.

A submerged membrane bioreactor has been operated at the laboratory scale for the treatment of a synthetic effluent containing Bisphenol-A (BPA). COD, NH4-N, PO4-P and BPA were eliminated respectively, at 99%, 99%, 61% and 99%. The increase of volumetric loading rate from 0 to 21.6 g/m(3)/d did not affect the performance of the MBR system. However, the removal rate decreased rapidly when the BPA loading rate increased above 21.6 g/m(3)/d. The adsorption process of BPA on the biomass was very well described by Freundlich and Langmuir isotherms. Subsequently, biodegradation of BPA occurred and followed the first order kinetic reaction, with a constant rate of 1.13 ± 0.22 h(-1). During treatment, membrane fouling was reversible in the first 84 h of filtration, and then became irreversible. The membrane fouling was mainly due to the accumulation of suspended solid and development of biofilm on the membrane surface.

Photo-degradation of butyl parahydroxybenzoate by using TiO2-supported catalyst.

The present work evaluates the potential of the photocatalysis (PC) process for the degradation of butylparaben (BPB). Relatively high treatment efficiency was achieved by comparison to photochemical process. Prior to photocatalytic degradation, adsorption (AD) of BPB occurred on the titanium dioxide (TiO2)-supported catalyst. AD was described by Langmuir isotherm (KL = 0.085 L g(-1), qm = 4.77 mg g(-1)). The influence of angle of inclination of the reactor, pH, recirculation flow rate and initial concentration of BPB were investigated. The PC process applied under optimal operating conditions (recirculation flow rate of 0.15 L min(-1), angle of inclination of 15°, pH = 7 and 5 mg L(-1) of BPB) is able to oxidize 84.9-96.6% of BPB and to ensure around 38.7% of mineralization. The Langmuir-Hinshelwood kinetic model described well the photocatalytic oxidation of BPB (k = 7.02 mg L(-1) h(-1), K = 0.364 L mg(-1)).